1. Field of the Invention
The present invention relates generally to the field of digital signal processing, and more specifically to the field of accurately storing, reproducing and synchronizing video and/or audio signals.
2. Description of the Background Art
In the video signal processing field, special challenges are presented where a variety of video signals are to be processed and combined. For example, a broadcaster such as The Weather Channel may wish to present a viewer with a composite image comprising a live video feed from a nationally-known landmark and a computer-generated graphic overlay, including forecasted high and low temperatures across the country.
Complications and opportunities to enhance the viewing experience in this exemplary scenario arise in at least two particularly relevant respects. First, where one signal is lost or interrupted, there is a need to preserve the quality of the overall image, and thereby maintain the usefulness of the second signal and the attention of the viewer. If, for example, the live landmark feed is lost, the user may be more likely to continue viewing the graphic data feed if a high-quality repetition of some segment of the already-displayed background feed is quickly substituted for the lost signal.
Second, when such a failure occurs, or even when both signals are fully functional and processed as intended by the broadcaster or system designer, it is desirable to maximize the quality of the composite image by properly synchronizing the two (or some greater plurality) of signals and, where appropriate, reproducing any stored signal as accurately as possible.
There is therefore a need in the art of digital signal processing for a method and system of accurately storing, reproducing and synchronizing audio and video data signals.
To address the shortcomings of the available art, the present invention provides a method and system for storing digital sampling data, such as sampling clock signal phase and frequency (referred to generally herein as decoder reference signal or xe2x80x9cDRSxe2x80x9d data), along with commonly stored pixel-related data such as luminance (e.g., the xe2x80x9cYxe2x80x9d component of a YCrCb signal) and chrominance (the xe2x80x9cCxe2x80x9d signal component), in order to offset common signal decoding and re-encoding errors, such as ringing, overshooting, cross-chrominance and cross-luminance.
It is therefore a first advantage of the present invention to provide a method and system for storing and utilizing information related to how data is manipulated, such that the manipulated data may be more accurately returned to its original form.
A second advantage of the present invention is the reduction of the occurrence of common decoding and re-encoding signal flaws, such as ringing, overshooting, cross-chrominance, cross-luminance, and high differential phase levels, by precisely storing and utilizing the original decoding phase and frequency information when a decoded signal is re-encoded.
It is a further advantage of the present invention to provide a method and system for linking the pixel clocks of a plurality of signals to ensure the signals are substantially synchronized.
It is a still further advantage of the present invention to provide a method and system providing synchronization of a plurality of signals, substantially reducing timing errors without a phase lock loop.
It is therefore a still further advantage of the present invention to provide a method and system for synchronizing a plurality of signals by periodically controlling a first signal""s reference source, such as a pixel clock, to control the timing of a second signal. In a preferred embodiment, the first signal""s reference source is a pixel clock signal gated to be accessed only when either of the vertical or horizontal synchronization signals is active and a field match is found.
It is yet another advantage of the present invention to provide a method and system for gating a first signal""s pixel clock signal in a manner based upon reducing the anticipated pixel count for the signal sufficient to mitigate any timing difference between the first and second signals during a predetermined period. In a preferred embodiment, the pixel count is decreased by the number of pixels contained in one line less than the actual line count of the signal, the predetermined period being one vertical scan time.
Still another advantage of the present invention is the provision of a method and system for selectively utilizing phase and frequency information relative to the digitization of a first signal when re-encoding the first signal or a modified version of the first signal.